You can do the entire door, heck, you could do the whole truck. but doing the whole truck by hand would be hard, and your arm would fall off LOL!
your arm will be sore after, trust me. I said do it by hand, because I am not sure if you have any experience with a buffer.

 

i have some experience from waxing the truck with the buffer. its hell of a lot easier then by hand and theres definitely a difference in quality using the buffer. i feel like the wax last longer. im probably gonna run out and get some polish compound today. any suggestion on brands?

 

if you are wetsanding the clear, you can wetsand it all.
This is a pretty good step by step
How to Wet Sand a Clear Coat: 9 Steps - wikiHow

 

Interesting reading! The clearcoat on my two-tone '98 LT (white with copper (I guess) along the bottom) was flaking off badly in the copper areas along the bottom of the driver's door and both front wheel arches (nearly perfect everywhere else). I coaxed it off the entire door area using a razor blade and soapy water. It was pretty easy since it was really badly bubbled. After, it looked a little faded in comparison to the un-flaky areas so I gave it a light hand-buff with polishing compound and it darkened up a bit. Been meaning to spray some clearcoat over it but I'm glad I read this first. The wheel aches were not quite as bad so I have, maybe, 25% of the area that still has the original 'coat firmly sticking so I did not want to disturb it. I'm hoping the zig-zag edges won't be too visable after the spray is applied. Guess I'll have to do this inside the garage since the drying time is so long.